GENERAL PROPERTIES: THE CORPUSCLES. 



405 



quantitative determination of the iron. The amount of oxygen 

 with which hemoglobin will combine may be expressed by saying 

 that one molecule of oxygen will be fixed for each atom of iron in the 

 hemoglobin molecule. In the decomposition of hemoglobin into 

 globin and hematin, which has been spoken of above, the iron is 

 retained in the hematin. 



Crystals. Hemoglobin may be obtained readily in the form of 

 crystals (Fig. 171). As usually prepared, these crystals are really 

 oxyhemoglobin, but it has 

 been shown that reduced 

 hemoglobin also crystallizes, 

 although with more diffi- 

 culty. Hemoglobin from 

 the blood of different ani- 

 mals varies to a marked 

 degree in respect to the 

 power of crystallization. 

 From the blood of the rat, 

 dog, cat, guinea pig, and 

 horse, crystals are readily 

 obtained, while hemoglobin 

 from the blood of man and 

 of most of the vertebrates 

 crystallizes much less easily. 

 Methods for preparing and 

 purifying these crystals will 

 be found in works on phys- 

 iological chemistry. To ob- 

 tain specimens quickly for 

 examination under the mi- 

 croscope, one of the most 

 certain methods is to take 

 some blood from one of the 

 animals whose hemoglobin 

 crystallizes easily, place it 

 in a test-tube, add to it a 



few drops of ether, shake the tube thoroughly until the blood be- 

 comes laky, that is, until the hemoglobin is discharged into the 

 plasma, and then place the tube on ice until the crystals are 

 deposited. Small portions of the crystalline sediment may then be 

 removed to a glass slide for examination. According to Reichert, 

 the deposition of the crystals is hastened by adding ammonium 

 oxalate to the blood in quantities sufficient to make from 1 to 

 5 per cent, of the mixture. Hemoglobin from different animals 

 varies not only as to the ease with which it crystallizes, but in some 



Fig. 171. Crystallized hemoglobin (after 

 Frey) : a, b, Crystals from venous blood of man : 

 c, from the blood of a cat ; d, from the blood of 

 a guinea pig; e, from the blood of a hamster; 

 /, from the blood of a squirrel. 



